Study on multi-period palaeotectonic stress fields simulation and fractures distribution prediction in Lannigou gold mine, Guizhou

A significant controlling factor for gold mineralisation is the tectonic stress field, and the fractures formed under its action are the migration channels and ore-holding spaces of ore-forming fluids, which often directly control the migration and accumulation of ore-forming fluids. Therefore, performing quantitative prediction research on the distribution of fractures in the Guizhou, Lannigou gold deposit in order to identify potential fluid flow pathways is of utmost importance for ore prospecting in practical. In this study, a 3D geological entity model was generated based on the GOCAD platform by analysing and processing the geological data of the studied area, as well achieved is the accurate characterisation of the study area’s geometric model. By integrating regional tectonic evolution history analysis, geological interpretation, rock mechanics experiments and acoustic emission testing, the finite element method was utilised to create a 3D geomechanical model of the research area, the paleotectonic stress field after the Indosinian and Yanshanian movements were superimposed was simulated, in associated with the rock failure criterion, the comprehensive fracture rate parameter (Iz) is introduced to predict the fracture distribution. The results show that the research area’s maximum principal stress is primarily distributed between 153.85 and 189.53 MPa, and the maximum shear stress is between 83.53 and 98.42 MPa. The spatial distribution of faults influences the stress distribution characteristics significantly, and the stress level is relatively high at the intersection of the fault, the end of the fault and the vicinity of the fault zone, and the stress value between the faults is relatively low. The tectonic stress field primarily controls the distribution and development of fractures, which is usually consistent with the areas with high values of maximum principal stress and maximum shear stress. Using the combined modeling technique of GOCAD and midas GTS to realize the conversion from 3D geological model to geomechanical model, a set of comprehensive fracture distribution prediction technique for the superposition of multi-stage tectonic stress fields of mineral deposits in complex tectonic areas has been formed, and provide a reference for the prediction of fracture distribution in similar complex structural areas.This study was supported by the program of China Scholarships Council (No. 202006670005); the National Natural Science Foundation of China (Project Nos. 51964007, 52264004, 52104080, 41962008); the Guizhou Province Science and Technology Support Program Project (Number: QIANKEHE Support [2021] General 516); Scientific and Technological Innovation Talents Team in Guizhou Province (Project No. [2019]5619); the Guizhou Province Highlevel Innovative Talents Training Project (Grant No. JZ2016-4011). Major Collaborative Innovation Project for Strategic Action of Mineral Search Breakthrough in Guizhou Province ([2022] ZD005); Natural Science Special (Special Post) Scientific Research Fund Project of Guizhou University (Project No. Guizhou University Special Post (2021) 51).Peer ReviewedPostprint (published version

Joint analysis of three genome-wide association studies of esophageal squamous cell carcinoma in Chinese populations

We conducted a joint (pooled) analysis of three genome-wide association studies (GWAS) 1-3 of esophageal squamous cell carcinoma (ESCC) in ethnic Chinese (5,337 ESCC cases and 5,787 controls) with 9,654 ESCC cases and 10,058 controls for follow-up. In a logistic regression model adjusted for age, sex, study, and two eigenvectors, two new loci achieved genome-wide significance, marked by rs7447927 at 5q31.2 (per-allele odds ratio (OR) = 0.85, 95% CI 0.82-0.88; P=7.72x10−20) and rs1642764 at 17p13.1 (per-allele OR= 0.88, 95% CI 0.85-0.91; P=3.10x10−13). rs7447927 is a synonymous single nucleotide polymorphism (SNP) in TMEM173 and rs1642764 is an intronic SNP in ATP1B2, near TP53. Furthermore, a locus in the HLA class II region at 6p21.32 (rs35597309) achieved genome-wide significance in the two populations at highest risk for ESSC (OR=1.33, 95% CI 1.22-1.46; P=1.99x10−10). Our joint analysis identified new ESCC susceptibility loci overall as well as a new locus unique to the ESCC high risk Taihang Mountain region

Energy Evolution Analysis of Coal Fracture Damage Process Based on Digital Image Processing

Coal rocks often contain calcite, which has a significant effect on the mechanical properties of coal and the energy evolution during rupture damage. In this study, the meso-scale of rock is considered, and the spatial distribution of the internal structure of coal is characterized by digital image technology. Uniaxial compression tests were conducted using RFPA on coal rocks containing calcite veins with diverse dip angles. The research results show that the different azimuth angles of the calcite veins change the internal stress distribution of the coal, resulting in higher coal compressive strength at low dip angles (0°, 15° and 30°). Under high dip angles (45°, 60°, 75° and 90°), coal has lower compressive strength. The fracture mode of coal is significantly affected by calcite. At low dip angle, the fracture mode of coal and rock is complex, which are inclined Z-type (0°), V-type (15°) and inverted V-type (30°), respectively. At high dip angle, the fracture mode of coal and rock is single, which is type I failure mode. The destruction process of coal rocks is influenced by calcite veins. Under low dip angle, the internal stress distribution of coal is relatively uniform, the weak cementation between matrix and calcite vein in coal is not easy to be damaged, the stress required for coal failure is large and the input energy, accumulated elastic energy and impact energy index are large. Under high dip angle, the internal stress distribution of coal is uneven, the weak cementitious material between matrix and calcite vein in coal is easy to be damaged and the input energy, accumulated elastic energy and impact energy index are small

Energy Evolution Analysis of Coal Fracture Damage Process Based on Digital Image Processing

Coal rocks often contain calcite, which has a significant effect on the mechanical properties of coal and the energy evolution during rupture damage. In this study, the meso-scale of rock is considered, and the spatial distribution of the internal structure of coal is characterized by digital image technology. Uniaxial compression tests were conducted using RFPA on coal rocks containing calcite veins with diverse dip angles. The research results show that the different azimuth angles of the calcite veins change the internal stress distribution of the coal, resulting in higher coal compressive strength at low dip angles (0°, 15° and 30°). Under high dip angles (45°, 60°, 75° and 90°), coal has lower compressive strength. The fracture mode of coal is significantly affected by calcite. At low dip angle, the fracture mode of coal and rock is complex, which are inclined Z-type (0°), V-type (15°) and inverted V-type (30°), respectively. At high dip angle, the fracture mode of coal and rock is single, which is type I failure mode. The destruction process of coal rocks is influenced by calcite veins. Under low dip angle, the internal stress distribution of coal is relatively uniform, the weak cementation between matrix and calcite vein in coal is not easy to be damaged, the stress required for coal failure is large and the input energy, accumulated elastic energy and impact energy index are large. Under high dip angle, the internal stress distribution of coal is uneven, the weak cementitious material between matrix and calcite vein in coal is easy to be damaged and the input energy, accumulated elastic energy and impact energy index are small

Experimental Study on the Stress Sensitivity and Influence Factors of Shale under Varying Stress

Shale reservoirs are characterized by extremely low permeability and high clay content. To further study the stress sensitivity of a shale reservoir, the Lower Cambrian shale in north Guizhou was utilized. Through laboratory testing, the relationships between the shale porosity and permeability and the effective stress were established, and the stress sensitivity of shale was analysed. The mechanical properties and mineral composition of this shale were studied by rock mechanics testing and X-ray diffraction. The main factors affecting the stress sensitivity were analysed. The results show that the porosity and permeability of this shale decrease with increasing effective stress; the shale reservoir permeability damage rate is 61.44 ~ 73.93%, with an average of 69.92%; the permeability stress sensitivity coefficient is 0.04867 ~ 0.05485 MPa−1, with an average of 0.05312 MPa−1; and the shale reservoir stress sensitivity is strong. Shale stress sensitivity is related to the rock mineral composition and rock mechanical properties. The higher the clay content in the mineral composition, the lower the elastic modulus of shale, the higher the compressibility, and the greater the stress sensitivity coefficient